Flat radiant-wall furnace and gas burner



Max-chr 3, 1964 R. L. wlLLoTT 3,123,127

' FLATRADIANT-WALL FURNACE AND GAS BURNER Filed March 2e, 195e 2 sheets-sheet 1 March 3, 1964 R. L. wlLLo'rT 3,123,127

FLAT RADIANT-WLL FURNACE AND GAS BURNER Filed March 2e, 195s 2 sheets-sheet 2 United States Patent C) 3,123,127 FLAT RADIANT-WALL FURNACE AND GAS BURNER Roiand Lancaster Wiilott, Cefn-y-Bedd, near Wrexham,

Wales, assigner, hy direct and mesne assignments, to

Saiem-Brosius (England) Limited, Milford, near Derby,

England, a company of Great Britain Filed Mar. 26, 1956, Ser. No. 573,715 Claims priority, application Great Britain Mar. 29, 1955 2 Claims. (Cl. 15S- 7) 'Ilhe present invention relates to the burning of fluid fuel for heating furnace Wall surfaces and, more particularly, for heating interior wall surfaces of heat treatment furnaces.

One feature of the present invention comprises a method of burnin-g a fluid fuel for the generation of heat in which air and fuel are separately discharged along and in close proximity to a refractory surface to burn as a sheet o-f flame spread over the surface whereby the llame heats the surface so that an object to be heated may be heated primarily by radiation from the surface.

A further feature of the invention consists in discharging the air and fuel as interfacing layers, the fuel layer being preferably between the refractory surface and the layer of air. The fuel and air may be discharged fanwise, the extent of the fanwise discharge being up to 360. A further feature of the invention consists in discharging the fuel and air along a at or substantially flat refractory surface.

A heating apparatus according to the invention cornprises a refractory surface and means for separately feeding and separately discharging air and a lluid fuel along and in close proximity to the refractory surface to burn as a sheet of flame spread over the surface.

Thus the invention provides a heating apparatus in which fuel and air discharge nozzles are `disposed closely adjacent to one another and to a refractory surface and communicate respectively with separate ducts for the supply of air and of fluid fuel thereto and are shaped and directed to smoothly turn and then discharge the fuel and air along the refractory surface in close proximity to each other, and preferably as interfacing layers, to enable the fuel to burn as a sheet of flame spread over the surface. The nozzles :may have outlets to discharge the fuel and air in fanwise layers up to 360 in extent and the air nozzle preferably includes spaced apart walls defining an air flow passage which first gradually decreases in cross-sectional area and then gradually increases in cross-sectional area from said decreased area to the outlet of the passage. Because of this construction, the air nozzle functions to increase the velocity of air being discharged through the air nozzle, the operation being analogous to that of a venturi structure.

One advantage of the present invention is that cornbustion is facilitated and rendered more efcient, once the refractory surface has become hot, by the direction of the fuel and air along the heated refractory surface.

Because the fuel and air are separately discharged it is unnecessary to supply them under high pressure to avoid burnback so that not only can the fuel and air be supplied under relatively low pressure i.e., pressures of the order of 4 to 6 -water gauge, but they can be turned down to a relatively small fraction as low as 5% of the normal rate of discharge. The rate of discharge can be simply controlled by adjustment of the supply pressures and/or adjustment of the nozzles.

Since the fuel and air are discharged separately they can be supplied at relatively low pressure and discharged at relatively low velocity thereby rendering the ame more controllable from the point of view of maintaining "ice it in close proximity to the refractory surface even when the refractory surface is lla-t or substantially llat.

rThe use of separate ducts and nozzles for the supply of fuel and air enables relatively large volumes of fuel and air to be discharged at relatively low velocities through relatively large nozzle openings to produce a flame of considerable extent along the IWall of a furnace, e.g. of the order of 6 feet in diameter or 3 to 4 feet long, the relatively low discharge velocity enabling the flame to maintain itself in close proximity to a substantially flat furnace wall. Obviously, the fuel pressure and the air pressure may be varied through a practical range, the particular pressure, for a particular nozzle opening, being related to the length of llame desired.

The invention is capable of wide application but a particularly useful application of the invention is to the heating of heat treatment furnaces since by the discharge of air and fuel along a refractory internal surface or surfaces of a furnace the impingernent of ame on the charge to be heat treated may be avoided or substantially so. In other Words, the flame is located effectively between the charge and lthe refractory surface whereby the charge is heated primarily by radiation from the surface.

The invention is most readily applicable to the burning of gaseous fuels but it may be applied to the burning of liquid fuels. It is to be understood that the fuel which is separately discharge is raw fuel in the sense that it is substantially unmixed `with air at the time it is being discharged. Such raw fuel may contain a small amount of air or other impurities but additional air must be added to the raw fuel to form a combustible mixture. Thus, the practice of theppresent invention does not include discharging premixed fuel and air but, instead, raw fuel and combustion air are discharged separately and are then mixed.

The invention 4is further described by way of example with reference to the accompanying drawings in which:

FG. l is a longitudinal sectional View of a burner according to the invention showing fragmentarily a furnace wall through which it projects;

FlG. 2 is a view similar to FIG. 1 -of an alternative form of burner; and

FIG. 3 is a fragmentary sectional view illustrating one application of the invention to a heat treatment furnace.

The burner shown in the accompanying FIG. l has a casing formed of two parts 1 and 2 provided with anges through which they are Abolted together. The part l of Ithe casing is tubular and the 4discharge portion 4 thereof is cylindrical.

The burner projects through a furnace wall 5 shown fragmentarily, being preferably perpendicular to the interior surface 29 of the furnace wall as shown in FIG. 1, and is secured to the wall by a llange 6. A tubular partition '7 arranged concentrically Within the casing part 1 provides an air passage S therewithin and a gas passage 9 between itself and the casing part 1. Gas is fed to the passage 9 by a branch pipe 10 opening into the conical end portion of the casing part 1.

The tubular partition 7 is formed at its discharge end with an outward annular projection 11 which lies beyond the discharge end 12 of the casing portion 4 and which defines therewith an annular gas discharge nozzle 13. As can be seen from the drawings, FIG. 1 in particular, the outlet of gas discharge nozzle 13- is substantially flush with the interior surface 29 of furnace wall 5 and faces in a direction substantially parallel to said surface so that fuel discharged from said orifice travels as a thin layer in a direction substantially parallel to said surface.

Spiders .14, 15 are formed respectively lwith a central plain opening 16 and a central threaded opening 17 to receive a spindle 1S coaxial with the tubular partition 7 and wljch at its lefthand end supports a baffle or deflector element 19 of approximately mushroom shape lying adjacent to the discharge end of the tubular partition so as to define therewith an annular air discharge nozzle 26. As can be seen from the drawings (FIG. l in particular), the air discharge nozzle 2%* includes spaced apart walls defining an air flow passage which first gradually decreases in cross-sectional :area and then gradually increases in cross-sectional area from said decreased area to the outlet of the passage. By virtue of this construction, the air nozzle functions to increase the velocity of air being discharged through the air nozzle, the operation being analogous to that of a venturi structure. As can be seen from the drawings (FIG. l, for example), the outlet of air nozzle 2i) faces in a direction substantially parallel to interior surface 29 of furnace wall S so that air discharged from said outlet travels as a thin layer in a direction substantially parallel to said surface.

Spider 14 is slidable in the tubular partition 7 and spider l5 is fixed to the end of partition 7.

Air is fed to the burner through the mouth -21 of the casing part 2. To isolate the casing part 2 from the gas passage 9 a liexible diaphragm 22y extends between the righthand end of the partition 7 and the flanges of the casing parts 1, 2.

The spindle i8 extends through an opening 23 in the casing part 2 and engages towards its righthand end in a threaded opening 2d in a cap 2S secured by screws 26 to a boss 27 on .the casing part 2. The threads of the threaded opening 24 of the cap 25 are of opposite hand and of coarser pitch than those of the opening 17 of the spider 1S so that on rotation of spindle 18 by means of a hand wheel 2S the partition 7 will move axially in the same direction as but to a lesser extent than the spindle 18. It is apparent that movement of partition 7 changes the size of the discharge orifice of fuel nozzle 13, and that movement of spindle 18 changes the size of the discharge outlet of air nozzle 2%.

Air and fuel supplied to the nozzles 13 and 2d will be discharged therefrom in fanwise layers of 360 in extent over the internal surface 29 of the furnace wall 5, with the fuel layer being located between the air layer `and internal surface 2Q at discharge, and with the air layer mixing progressively with the fuel layer as the fuel travel-s dong said internal surface to produce a corn- -bustible mixture located in close proximity to said surface substantially throughout the extent of the combustible mixture so that burning of the mixture produces a thin sheet-like llame of substantial area spread over said internal surface and in close proximity thereto.

The burner illustrated in FlG. 1 is designed for use with gas. The burner illustrated in FIG. 2 is similar in many respects to that of HG. l but is designed for use rwith oilA fuel and the cylindrical discharge portion 4 of the casing part 1 is therefore formed with a water jacket 3d to cool it.

A spider 32 is secured to the righthand end of the tubular partition 7 and ay tube 33 secured in a central opening of the spider 32 passes through an opening 34 in the casing part 2. -A .collar 35 secured to the righthand end of tube 33 has an external annular groove 36 therein to receive a rider 37 which is forked for engagement in and around an upper portion of the groove 36. An adjusting screw 38 which is squared at its righthand end 39 is rotatable in but axially fixed relatively to bearing openings in spaced flanges dit, 41 of the casing part 2. The tubular partition 7 can thus `be axially displaced by adjustment of the screw 33 to enlarge or reduce the nozzle opening i3. i Y

The spindle 18 passes through the tube 33 and is threaded at its righthand end for engagement in a threaded cap 422 secured to the righthand end of the casing part 21. Thus the nozzles i3 and Ztl of the burner shown in the accompanying FIG. 2 can be independently adjusted by @c means of a hand wheel 43 `and the adjusting screw 38.

FIG. 3 illustrates one application of the present invention to a heat treatment furnace in which a nozzle 44, which may be similar to the nozzles described with reference to FGS. l and 2, discharges fuel and air in fanwise layers substantially radially therefrom as indicated by the arrows over a flat refractory wall sur-Y face 43.

I claim:

l. A furnace comprising a furnace wall having a substantially dat interior surface, a raw fuel duct extending through said `wall and terminating in a fuel nozzle located within said furnace closely adjacent said surface, said fuel nozzle including spaced apart wall members defining an annular fuel discharge orifice extending throughout an arc up to 360, said orifice being substantially flush with said surface and facing in a direction substantially parallel Y to said surface so that fuel discharged from said orifice travels as a thin layer in a direction substantially parallel to said surface, at least one of the wall members defining said fuel discharge onifi being movably supported for varying the size of said fuel discharge orifice, an air duct extending through said lwall and terminating in an air nozzle located within said furnace closely adjacent and'V beyond said fuel nozzle, said air nozzle including spaced apart wall members den-ing an annular air flow passage extending throughout an arc up to 360, said passage first gradually decreasing in cross-sectional area, and then gradually increasing in cross-sectional area from said def creased area to the outlet of said passage whereby said air nozzle functions to increase the velocity of air passing through said air nozzle, said air outlet facing in a direction substantially parallel to said surface so that air discharge from said air nozzle outlet travels as a thin layer in a direction substantially parallel to said surface and Y passage outlet, adjusting means connected to said movably" Y supported fuel discharge orifice Wall member for varying the size of said fuel ydischarge orifice, and adjusting means connected to said movably supported air ilow passage .1

wall member for varying the size of said air Ypassage outlet.

2. A furnace comprising a furnace wall having a substantially dat interior refractory surface, an air duct eX- tending through said wall and terminating in an air nozzle located Within said furnace closely adjacent saidsurface, a raw fuel duct surrounding said air ductand also extending through said wall and terminating in a fuel nozzle located within said furnace closely adjacent said surface and between said air nozzle and said surface, both said air nozzle and said fuel nozzle including spaced apart wall members defining an annular fuel discharge outlet positioned substantially flush with said surface andYcommunicating with said fuel duct and anV annular air discharge outlet communicating with said air duct with one of said wall members being Acommon to both said fuel'V nozzle and said air nozzle, both said fuel outlet and said air outlet facing in a direction substantially parallel to said interior refractory surface so that fuel and air discharged from said outlets travel as thin layers in a direction sub? stantially parallel to and along said surface, with the fuel being located between the air and said surface andwith.

the air and fuel mixing progressively as they-travel Where- Vinf by a sheet-like flame of substantial area may be profV duced, means supporting said common wall member'ifor move ent ina direction axially of said fuel duct for varyA ing the size of Said fuel discharge outlet, means support-17VY ing the other Wall member defining said air outlet for movement in a direction axially of said air duct for varying the size of said air outlet, and a `eommon adjusting means connected to both said movably supported common wall member and said movably supported other Wall member, both `of said movably supported Wall members' being movable simultaneously in response to actuation of said common adjusting means -to simultaneously vary the size of said fuel and air outlets.

105,558 Ells July 19, 1870 6 Brown Apr. 15, 1930 Friedman Feb. 9, 1932 McCutcheon et al June 6, 1933 Oone Mar. 6, 1934 Hopkins June 5, 1945 Swenson et al Oct. 23, 1951 Getz et a1. Ang. 21, 1956 FOREIGN PATENTS Germany Nov. 22, 1932 Great Britain Feb. 3, 1927 Great Britain Mar. 1, 1943 Netherlands Feb. 15, 1949 

1. A FURNACE COMPRISING A FURNACE WALL HAVING A SUBSTANTIALLY FLAT INTERIOR SURFACE, A RAW FUEL DUCT EXTENDING THROUGH SAID WALL AND TERMINATING IN A FUEL NOZZLE LOCATED WITHIN SAID FURNACE CLOSELY ADJACENT SAID SURFACE, SAID FUEL NOZZLE INCLUDING SPACED APART WALL MEMBERS DEFINING AN ANNULAR FUEL DISCHARGE ORIFICE EXTENDING THROUGHOUT AN ARC UP TO 360*, SAID ORIFICE BEING SUBSTANTIALLY FLUSH WITH SAID SURFACE AND FACING IN A DIRECTION SUBSTANTIALLY PARALLEL TO SAID SURFACE SO THAT FUEL DISCHARGED FROM SAID ORIFICE TRAVELS AS A THIN LAYER IN A DIRECTION SUBSTANTIALLY PARALLEL TO SAID SURFACE, AT LEAST ONE OF THE WALL MEMBERS DEFINING SAID FUEL DISCHARGE ORIFICE BEING MOVABLY SUPPORTED FOR VARYING THE SIZE OF SAID FUEL DISCHARGE ORIFICE, AN AIR DUCT EXTENDING THROUGH SAID WALL AND TERMINATING IN AN AIR NOZZLE LOCATED WITHIN SAID FURNACE CLOSELY ADJACENT AND BEYOND SAID FUEL NOZZLE, SAID AIR NOZZLE INCLUDING SPACED APART WALL MEMBERS DEFINING AN ANNULAR AIR FLOW PASSAGE EXTENDING THROUGHOUT AN ARC UP TO 360*, SAID PASSAGE FIRST GRADUALLY DECREASING IN CROSS-SECTIONAL AREA, AND THEN GRADUALLY INCREASING IN CROSS-SECTIONAL AREA FROM SAID DECREASED AREA TO THE OUTLET OF SAID PASSAGE WHEREBY SAID AIR NOZZLE FUNCTIONS TO INCREASE THE VELOCITY OF AIR PASSING THROUGH SAID AIR NOZZLE, SAID AIR OUTLET FACING IN A DIRECTION SUBSTANTIALLY PARALLEL TO SAID SURFACE SO THAT AIR DISCHARGE FROM SAID AIR NOZZLE OUTLET TRAVELS AS A THIN LAYER IN A DIRECTION SUBSTANTIALLY PARALLEL TO SAID SURFACE AND MIXES PROGRESSIVELY WITH FUEL DISCHARGED FROM SAID FUEL DISCHARGE ORIFICE AS SAID FUEL TRAVELS ALONG SAID SURFACE TO PRODUCE A COMBUSTIBLE MIXTURE LOCATED IN CLOSE PROXIMITY TO SAID SURFACE SUBSTANTIALLY THROUGHOUT THE EXTENT OF THE COMBUSTIBLE MIXTURE WHEREBY BURNING OF SAID MIXTURE PRODUCES A THIN SHEET-LIKE FLAME OF SUBSTANTIAL AREA SPREAD OVER SAID SURFACE AND IN CLOSE PROXIMITY THERETO, AT LEAST ONE OF THE WALL MEMBERS DEFINING SAID AIR FLOW PASSAGE BEING MOVABLY SUPPORTED FOR VARYING THE SIZE OF SAID AIR PASSAGE OUTLET, ADJUSTING MEANS CONNECTED TO SAID MOVABLY SUPPORTED FUEL DISCHARGE ORIFICE WALL MEMBER FOR VARYING THE SIZE OF SAID FUEL DISCHARGE ORIFICE, AND ADJUSTING MEANS CONNECTED TO SAID MOVABLY SUPPORTED AIR FLOW PASSAGE WALL MEMBER FOR VARYING THE SIZE OF SAID AIR PASSAGE OUTLET. 